Speech and Gesture in Sync: Investigating Temporal Integration Across Childhood

Our hands rarely lie still while we talk. Some hand movements, like washing dishes or other household tasks, are often unrelated to what we express in speech. Other hand movements, known as gestures, are deeply integrated with verbal communication. Past research with adults has found strong temporal synchrony between speech and gesture, particularly as compared to speech and action. This evidence supports the claim that speech and gesture emerge from a single integrated system and suggests that gestures hold a unique status in communication compared to other kinds of hand movements. However, the developmental unfolding of this tight temporal integration is unknown. In this cross-sectional study, we directly measure the speech-gesture production system in childhood. In a within-subjects design, adults (N = 35; M_age = 19.94 years; range = 18-25 years) and children (N = 68; M_age = 8.38 years; range = 5-12 years) were asked to verbally describe how they use household objects while producing either gestures or communicative actions. Speech onset, action onset, and gesture onset were coded to determine the difference in onset between speech and movement (action or gesture). Results indicate that speech and gesture were produced in closer temporal synchrony than speech and action across all ages tested, showing remarkable stability in speech-gesture temporal relations over development. This lack of any notable developmental change in temporal synchrony between speech and gesture is consistent with the theory that speech and gesture emerged phylogenetically as an integrated cognitive system.